There are 6 US Post Offices in Morton County serving a total of 27,838 residents equating to 4,640 residents per post office. It's estimated that approximately 44,433 packages are handled across the 6 county post offices annually. Morton County is a county located in the U.S. state of North Dakota. As of the 2010 census, the population was 27,471, making it the seventh-most populous county in North Dakota. Its county seat is Mandan. The county was originally created in 1873 and later organized in 1878. Morton County is included in the Bismarck, ND, Metropolitan Statistical Area."